Caffeine synthase is a methyltransferase enzyme involved in the caffeine biosynthesis pathway. It is expressed in tea species, coffee species, and cocoa species. The enzyme catalyses the following reactions: S-adenosyl-L-methionine + theobromine S-adenosyl-L-homocysteine + caffeine + H+ S-adenosyl-L-methionine + paraxanthine S-adenosyl-L-homocysteine + caffeine + H+ 7-methylxanthine + S-adenosyl-L-methionine S-adenosyl-L-homocysteine + H+ + theobromine Caffeine synthase is expressed in the Camellia species irrawadiensis, ptilophylla, and sinensis; the Coffea species arabica, and canephora; and in Theobroma cacao. References EC 2.1.1 Caffeine Camellia